A fan device used with respect to a computing device. The fan device includes at least two fans that provide airflow for the computing device and a controller that adjusts the fans' speeds in an attempt to avoid harmonic vibrations of the at least two fans. The fan device may include at least one sensor, and the controller may adjust the fans' speeds based at least on information from the sensor(s) in the attempt to avoid the harmonic vibrations. The attempt to avoid the harmonic vibrations may also attempt to mitigate one or more of turbulence, pressure, over-heating, power consumption, or noise in, by, or around the computing device. Reversal of airflow may also be used. A fan bar that enables isolation of ground return noise may also be used. The controller may use sums of primes calculations, phase analysis, common divisor calculations, and the like. Also, associated methods.